Heat exchange apparatus



July 12, 1949. M. FRIsQH ET AL 2,475,604

HEAT EKCBHIGE APPARATUS Filed Nov. 2, 1943 5 sheets-sheet 1 July 12, 1949. M. FRlSC H ET L HEAT EXCHANGE APPARATUS 3 Sheets-Sheet 2 Filed Nov, 2, 1943 INVENTORS NAET/N Fe/JCH v 8.41am D July 12, 1949. scH ET AL HEAT EXCHANGE APPARATUS Filed Nov. 2, 1943 3 Sheets-Sheet 3 ATTOR Y itent ed July 12, 1949 UNITED STAT as PATENT OFFICE HEAT Examiner; APPARATUS Martin Frisch,

den City, N. Y.,

New York New York, and John Blizard, Garassignors to Foster Wheeler Corporation, New York, N. Y.,

a corporation of Application November 2, 1943, Serial No. 508,668

'6 Claims- (crest-462.16)

This invention relates to heat exchange appa-- ion with the accompanying drawings forming I. part thereof, and in which:

Fig. 1 is a vertical sectional view of an econonizer for a steam generator embodying the in- Iention;

Fig. 2 is a vertical )f Fig. 1;

Fig. 3 is a cabinet projection of an extended surfaceelement embodying the invention;

Fig. 4 is an elevational view, with parts in' sec-1 tion, of a tubular member with extended surface elements of the type shown in Fig. 2, welded" thereto;

Fig. 5 is a-view illustrating in an exaggerated manner, the action of the-hub of an extended sur-' face element of the typ'eishown in Fig. 3, while it is being welded to a tubular member; I

Fig. 6 is a cabinet projection of another form of extended surface element embodying the invention, and

sectional view on line 2-4 Fig. 7 is a longitudinal sectional view of a tubular member with extended surface elements therein which are adapted to be soldered to the tubular member.

Like characters of reference refer to the same or to similar parts throughout the several views.

Although the invention is disclosed as embodied in an economizer for a steam generator, it will be understood that it is not limited to this use, but is capableof application generally to the transfer of-heat.

Referring to the drawings, reference character i0 designates a casing for an economizerfor a steam generator, having an inner portion H forming a passage forproducts of combustion flowing from the steam generating and superheating sections of the generator, and outer portions 12- providing housings for the inlet and outlet headers and the return bend portions or connections'of the economizer. As shown, the casing I0 is attached to a steam and water drum l3 of the steam generator. Feed water is supplied to the economizer thro h an inlet connection it andJs conducted therefrom throuzh an outlet connection l5. i

The tubular members It of the economizer are provided with extended surface elements ll of the type shown in Figs. 3 and 4. Each element l'I consists of a hub l8 and a flange it which is integral with the hub at one end thereof, and extends transversely to the axis of the tubular member on which the element is mounted and is constructed and arranged to provide a plurality, sixteen as shown, of radially extending projections 2ll,'of isosceles trapezoidal configuration in the plane of the projections, the bases of which are spaced 9. short distance from the hub l8. The hub l8 has a plurality of spaced, longitudinally extending grooves 2I in the inner. portion thereof to aid in effectively welding the hubs to tubular members, as will presently appear.

' The extended surface elements, in the forms shown for use with steel tubular members, preferably are made of sheet ingot iron having a coeificient of thermal conductivity equal to or greater than that of the tubular members on which they are mounted. The term "ingot iron, as used herein, refers to an iron of high purity which contains generally less than 0.1% carbon. For steel tubular members of one and one-half inches in outside diameter, extended surface elements made from sheet ingot iron of approximately one-sixteenth inch thickness have been found satisfactory. It will be understood that these figures are given by way of example only and'without any limiting effect upon the invention.

The extended surface elements preferablyare secured to the tubular members by electric resistance seam welding the hubs iii of the elements to the tubular members, with the hub of one element in contact with the flange of the next ad- Jacent element as shown in Fig. 4, so that'the hubs will provide a covering for each tubular member to shield it from contact with the fluid flowing over the tubular members and the extended surface elements thereon. The major portions of the hubs preferably will be seam welded to the tubular member as indicated at 22 in Fig. 4.

The function of the grooves 2| in the interior of the hub [8 will be understood from a consideration of Fig. 5, wherein the seam welding electrode wheels are designated 25 and 26. ,Due to the pressure of the electrode wheels and to the necessity for clearance between the tubular member l6 and the hub l8 of the extended surface element, at the beginning of and in the early stages of the welding operation, the hub it will be forced into an elliptical shape asindicated inFig. 5,

with air gaps between the tube and the hub in the areas between the welded areas. Moreover, the hub will be heated ordinarily to a higher temperature than the tube, resulting in an expansion of the hub and an increase in its circumference as well as an increase in the air gaps. As the welding proceeds, the circumference of the hub will increase further, due to the plasticity assumed by the metal of the hub. The net result is to cause a shearing stress to be set up between the hub and the tube at the weld which may actually cause the weld to be partially broken as fast as it is made. The grooves 2| provide spaces into which the expanding-metal can be forced during welding and they also provide areas of local weakness in the hub so that the metal of the hub can be forced against the tube without deformation of adjacent parts of the hub. Thus the magnitude of the shearing stress is reduced with the result that the hub will tend to keep its original circular shape and the weld will be good. Use of the grooves 2| presents no disadvantage to welding, because a continuous surface is presented to the seam welding electrode wheels, thereby preventing arcing and deterioration of the wheels. I

Should it be desired to spot weld the hubs of the extended surface elements to the tubular members, the hubs it of the elements may be slotted longitudinally at intervals as indicated at 21 in Fig. 6, for the reasons mentioned in connection with the use of the grooves 2 I.

In lieu of welding the hubs of the extended surface elements to the tubular members, they may be secured by any other suitable means, if desired. For example, theyv may be secured by soldering or brazing. Fig. 7 illustrates a form of extended surface element which is particularly well adapted to be silver soldered to tubular members. Referring to Fig. 7, the hub 30 of each element, has an outwardly extending flange 3| at its outer end, which provides sufficient space with the outer surface of the tubular member to receive a ring of-silver solder 32. When soldering heat is applied, the solder will melt and will flow 1 into the space between the hub and the tubular member and will secure the element to the tubular member. Any suitable solder may be employed, and the flange 3| need not necessarily be utilized for effective soldering. Preferably, the hub 30 will be continuous and without grooves or slots, for soldering or brazing.

Extended surface elements having a plurality of projections such as the projections 20, are superior from a heat transfer standpoint to a continuous disc of the same diameter and thickness because (a) turbulence of the fluid flowing overthe elements is greater with the discontinuous,

surface, (b) the surface area per unit weight of metal is greater due to the greater edge area, and (c) the least efficient heat transfer surface near the outer periphery of the element is removed, so that the element is made lighter with less than a proportional loss of heat recovering ability.

'Ihenumber and shape of the projections 10 may be varied as desired, and may be of an even or an odd number. However experiments have shown that the rate of heat absorption per unit of surface of an element of a given thickness increases as the number of projections increases.

The grooves 2| and slots 2'! in the hubs of the extended surface elements may be omitted, if desired, and in some circumstancesthe hub itself need not be used. If the hub is not utilized. the flange with the plurality of projections will be tubular member without into which metal of the secured to the, tubular member by any suitable means, such as welding, soldering, brazing. or the like. i

The forms of the invention disclosed herein are to be considered as preferred forms. and the invention is not to be limited excepting by the scope of the appended claims.

What is claimed is:

1. An extended surface element for a tubular member of a heat exchange device comprising a metallic hub adapted to be mounted on and welded to the tubular member and a plurality of projections in heat exchange relationship with and extending outwardly from the hub, the hub having a plurality of grooves in its inner peripheral portion circumferentially spaced from one another around said periphery and extending substantially parallel to the axis of the hub, the num-- her, size and depth of said grooves being such as to provide areas of local weakness in the hub into which metal of the hub expands during welding and such that the hub can be forced against the tubular member without deformation of adjacent parts of the hub.

2. An extended surface element for a tubular member of a heat exchange device comprising a metallic hub adapted to be mounted on and welded to the tubular member and a plurality of projections integral with and extending outwardly from the hub, the hub having a plurality of spaced grooves in its inner peripheral portion circumferentially spaced from one another around said periphery and extending substantial ly parallel to the axis of the hub, the number, size and depth of said grooves being such as to provide areas of local weakneess in the hub into which metal of the hub expands during welding and such that the hub can be forced against the deformation of adjacent parts of the hub.

3. An extended surface element for a tubular member of a heat exchange device comprising a metallic hub adapted to be mounted on the tubular member in heat transfer relationship and a plurality of projections of heat conducting material and of isosceles trapezoidal configuration in a direction normal to the axis of thehub and integral with the hub and extending outwardly therefrom at one end thereof and disposed approximately in a plane extending substantially transversely to the-axis of the hub, the hub being adapted to be welded to the having a plurality of spaced grooves in its inner peripheral portion circumferentially spaced from one another around said periphery and extending substantially parallel to the axis of the hub, the number, size and depth of said grooves being such as to provide areas of local hub expands during welding and such that the hub can be forced against the tubular member without deformation of adjacent parts of the hub. 1

4. Heat exchange apparatus comprising a tubular member and an extended surface element for the tubular member having a hub electric resistance seam welded thereto and a plurality of projections of isosceles trapezoidal configuration in a direction normal to the axis of the hub, the projections extending outwardly from the hub at one end thereof and being disposed approximately in a plane extending substantially transversely tubular member and weakness in the hub I iner peripheral portion circumterentially spaced :om one another around said periphery and exanding substantially parallel to the axis of the .ub prior to the welding of the hub to the tubular iember, the number, "size and depth of said rooves being such as to provide areas of local weakness in the hub into which metal of the hub xpands during welding and such that the hub an be forced against the tubular member withlut deformation of adjacent parts of the hub.

5. In an economizer for a steam generator :omprising a plurality of spaced tubular members n communication with one another to form a luid flow path, said flow path having a fluid inlet it one end thereof and a fluid outlet at the oppoaite end thereof, an extended surface element-tor ;he tubular members having a hub electric re- ;istance seam welded thereto and a plurality of projections of isosceles trapezoidal configuration in a direction normal to the axis of the hub, the projections extending outwardly from the hub at one end thereof and being disposed approximately in a plane extending substantially transversely to the axis of the hub, the element being composed of ingot iron having a higher thermal conductivity than that of the tubular member, the hub having a plurality of spaced grooves in its inner peripheral portion circumferentially spaced from one another around said periphery and extending substantially parallel to the axis of the hub prior to the welding of the hub to the tubular member, the number, size and depth of said grooves being such as to provide areas of local weakness in the hub into which metal of the hub expands during welding and such that the hub can be forced against the tubular member without deformation of adjacent parts of thehub.

6. An extended surface element for a tubular member of a heat exchange device comprising a metallic hub adapted to be mounted on and welded to the tubular member, heat conducting neans extending outwardly from and in a direcion normal to the axis of th hub, the hub MARTIN FRISCH. JOHN BLIZARD.

REFERENCES CITED file of this patent:

UNITED STATES PATENTS Number Name Date 1,865,051 Trane June 28, 1932 1,893,270 Caldwell Jan, 3, 1933 1,916,574 Key July 4, 1933 25 1,992,646 Young Feb. 26, 1935 2,085,041 Reigart et al. June 29, 1937 2,089,340 Cobb Aug. 10, 1937 2,261,136 Brown, Jr. Nov. 4, 1941 2,216,778 Houdry ...Oct. 8, 1940 FOREIGN PATENTS Number Country Date 7,242 Great Britain 4-..--- June 13, 1885 3,026 Great Britain Nov. 23, 1905 35 331,392 Great Britain July 3, 1930 502,579 Great Britain Mar. 21, 1939 574,566 France July 16, 1924 OTHER REFERENCES iaving grooves in its inner peripheral portion The Metals Handbook, 1939 edition, page 7.

Chemical Engineer's Handbook, 2nd edition, John Perry, editor, 1941. Page 949.

The Metal Iron, by H. E. Cleaves and J. 0.

Thompson, 1935, page 71.

The following referenices are of record in the 

